Carbon rheostat



Dec. 22, 1931. Y P. E. KLOPSTEG 1,837,554

CARBON RHEOSTAT Filed Feb. 16, 1929 Patented Dec. 22, 1931 UNITED STATESFF l -cl I PAUL E. KLOPSTEG, or CHICAGO, ILLINOIS, AssIe oa. rocEi raALscmumrc 'com PANY, or CHICAGO, ILLINOIS, AICORPORAT'ION on LLIN IsCARBON Itnizos'mr This invention relates to carbon rheostats and has forits principal object to increase the I stable range, the precision ofadjustment and the ability to dissipate heat. p Further objects andadvantages of the invention will become apparent as the disclosureproceeds and the description is read in connection with the accompanyingdrawings illustrating a preferred embodiment of the in- 1 vention, andin which Fig. 1 is a side elevation of a carbon rheostat having somewhatfamiliar characteristics but embodying this invention, the intermediateportion of the rheostat being broken away;

17, Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1; and

Fig. 3 is a perspective View illustrating the manner of associating thecarbon and metal plates.

:1) But this specific illustration and the corresponding description areused for the purpose of disclosure only and are not intended to definethe limits of the invention, for I realize that it may be embodied inother forms.

The frame of the rheostat comprises end castings and 11 rigidlyconnected in spaced relation by rods 12, 13 and 14 equipped with nuts15. The trough is formed by two bars 16 and 17 of heat resistinginsulating material such as asbestos slate, the ends of which aresupported on inwardly directed inclined lugs 18 and 19 which support thebars 16 and 17 with their lower edges separated to leave the bottom ofthe trough open. 1

Arranged in the trough on edge with their diagonals horizontal andvertical are a series of square plates 20 of hard carbon. At the ends ofthe series are square plates 21 of metal equipped with terminals 22.Outside the plates 21 are heat resisting insulating plates 23, one ofwhich bears against the inner side of the casting 11 and the otherreceives the thrust of a screw 24 equipped at its inner end with apressure plate 25. The screw 24 is threaded in a boss 10a on the casting1 0 and its outer end is fitted with a knob or hand wheel 26.

Interposed between adjacent carbon plates operations.

20=are metal plates snhstantiallyrectaniguilar in shape,'with' onedimension equal to a side of'the square plates 20. At one lower cornerthe plates 27 have rectangular? projections 28 which extend through thebottom of the trough'as best illustrated in Fig. 2.

The metal plates may he made of a'variety of materials and in a varietyof terms. Steel,

.005 of an inch thick h'avebeen found very satisfactory. They shouldhave sufficient flexibility to yield readily under pressure ofthescrew24 and shoul'd have sufficient resiliency to promptly expand theseriesof plates rangedin two series-asbest illustrated-inFig. '2,adjacent plates being in alternate series.

As shown in the drawings, the convex faces ofthe resilient plates inOIIBSBI'IGS- all facein the same direction, while the convex facesof theother series face in the opposite direction. This will overcome thetendencyofthe col-- umn ofplat'es to buckle and will a fio'rdbetterradiation.

The rheostat is used in the usual manner and" adjustments are made byturning the screw 24." An old type carbon rheostat of familiarconstruction will give resistance" up to six or elght' ohms, but attheir higher valu es the resistance varies greatly in fdifierenterratic. Such a rheostat, equippedwith metal plates 27, will have aresistance up to'forty or fifty ohms with fixed values'at any setting ofthe screw within the range or the device.

It will also dissipate heat two or three times j as. rapidly, and sincethefrcsistanceof carbon decreases as the heat rises, even the heatradiation of the improved? structure becomes an important advantage. V

The heat generated by the current is rapidly conducted to those portionsof the metal plates 27 that extend beyond the carbon plate,

nickel and phosphor-bronze from .003 to Its action may bedescribed asand by those portions to the air surrounding them, thus producingconvective currents traversing'radiating surfaces of great area. mo

In the form shown in the drawings, there are in effect four radiators ofgreat area and high efficiency.

I claim as my invention:

1. In a carbon rheosta-t of the type including a number of carbon platesarranged side by side, and means for pressing the plates together withvariable pressure, the combination of curved resilient metal platesinter posed between adjacent carbon plates and arranged in twolongitudinal series angularly disposed with respect to each other, andprojecting laterally beyond the margins of the carbon plates.

2. In a carbon rheostat of the type including a number of carbon platesside by side in a trough and means to vary the pressure between theplates, the combination of curvel resilient metallic plates interposedbetween adjacent carbon plates and arranged in two longitudinal serieswith the axes of curvature in the series at an angle.

3. In a carbon rheostat, a trough including two plates inclinedoppositely from the vertical and spaced apart at their lower edges, anumber of carbon plates side by side in the trough, resilient metalplates interposed between adjacent carbon plates and projecting throughthe bottom of the trough in alternate series angularly disposed withrespect to each other, and means to vary the pressure on the plates.

4. In a carbon rheostat, a trough including twoplates inclinedoppositely from the vertical and spaced apart at their lower edges, anumber of carbon plates side by side in the trough, resilient metalplates interposed between adjacent carbon plates and projecting throughthe bottom of the trough, said carbon and resilient plates beingarranged in two longitudinal series at an angle with each other andhaving adjacent resilient plates in alternate series, and means to varythe pressure on the plates.

5. In a carbon rheostat of the type including a substantially opentrough and a number of carbon plates arranged side by side therein, thecombination of curved resilient metal plates interposed between theseveral carbon plates and arranged so that the convex faces of alternateresilient plates face in one direction while the other resilient plateshave their convex faces facing in the opposite direction to preventbuckling of the combina tion of plates, and means for varying thepressure on the plates.

In testimony whereof I aflix my signature.

PAUL E. KLOPSTEG.

